Power generation plants for producing electric power often comprise combined cycle power plants to meet the needs of efficient and flexible power production. Combined cycle power plants typically combine a steam turbine system with a gas turbine engine connected to generator. In particular, the waste heat from the gas turbine engine may be used to generate steam, such as in a heat recovery steam generator (HRSG), and the steam may be supplied to the steam turbine for generation of additional electrical energy. Hence, otherwise unused energy in the form of waste heat from the gas turbine engine may be converted into an additional energy output through the steam turbine system.
Various approaches have been proposed to further increase the efficiency and/or work output of combined cycle power plants. For example, with regard to the efficiency of the gas turbine engine, the overall efficiency of the gas turbine engine may vary as a function of the compressor and turbine efficiencies, ambient air temperature, turbine inlet temperature and the overall pressure ratio. Efficiencies in the engine may be increased by operating the compressor at lower gas temperatures, operating the turbine at higher gas temperatures, and operating at a higher overall pressure ratio. With regard to the steam turbine system, additional efficiencies may be obtained by improving the conversion of thermal energy from the gas turbine engine exhaust to usable energy in the form of steam in the HRSG.